1. Field of the Invention
The present invention relates to an ink jet recording apparatus having a member for cleaning the ink deposited onto the surface of an ink jet head for recording by discharging the ink.
2. Related Background Art
In ink jet recording apparatuses for recording with an ink jet head which discharges the ink onto a recording medium, the ink mist produced by the discharging of ink or the ink mist splashed away from ink droplets impinging on the recording sheet may sometimes adhere to an ink discharge port area of the ink jet head or a head surface having discharge ports formed thereon, or alien substances such as paper powders or dirts may deposit thereto via the wet ink, thereby blocking some discharge ports. In such a case, even if the recording is then made, the discharge direction of the ink may vary owing to the effects of adherent matters, causing a discharge failure, or making impossible the discharge to lead to the abnormal recording.
In conventional ink jet recording apparatuses, there is provided a cleaning member (cleaning blade) for wiping the discharge ports a non-recording region, with which adherent matters are cleaned away by rubbing a discharge port formation face against said cleaning member by utilizing the movement of a carriage having the head mounted thereon. This art is important in improving the recording characteristics of the ink jet recording apparatus or enhancing the reliability.
Also, because adherent matters such as paper powders or dirt may not be removed by this cleaning operation, or foreign matters may enter some discharge ports, there is provided a recovery device composed of a suction cap and a suction pump to suck away these contaminants together with the ink through discharge ports due to a negative pressure of the pump.
On the other hand, to control properly the interval (a so-called paper distance) between an ink jet head and the surface of a recording member (recording sheet) in performing the printing is also an important art for maintaining the high-quality image in the ink jet recording apparatus. When the paper distance is too great, the impinging point may be greatly displaced due to deflection in the jetting direction of ink droplet, resulting in conspicuous distortions of the image with lesser image. Conversely, if the paper distance is too close, the recording head may be rubbed against the recording sheet due to deformation (so-called cockling) of the recording sheet after printing, disordering the image, or damaging the recording head to bring about the abnormal discharge, so that a nonconformity such as degraded quality image occurs at times.
In an ink jet recording apparatus which allows for the use of a plurality of kinds of recording sheets, the adjustment of paper distance is particularly important because the paper interval will greatly vary depending on the difference in the thickness of recording sheet, or the degree of cockling.
Thus, in conventional ink jet recording apparatuses, the adjustment of the paper interval relative to the head was conducted by changing automatically or manually the position of a carriage for holding the ink jet head at a multiplicity of stages so as to adjust the paper interval to a proper value.
FIG. 4 shows a perspective view of an ink jet recording apparatus having a wiping member and a suction device and provided with means for changing the position of carriage, and FIG. 5 shows a schematic view of a portion around the carriage and the recovery device.
In FIG. 4, 1 is a recording head, 2 is a carriage, 31 is a carriage guide pipe for supporting the carriage, and 32 is a carriage rail guide for determining the distance between the carriage and a platen by coming into contact with the bottom face of carriage, in which the carriage position can be determined by 31 and 32. Numeral 4 is a platen for supporting the print face of a recording sheet.
Recording means 1 as shown in the figure is one example of color recording means, and the carriage 2 has four recording heads with different color inks mounted thereon. Four ink colors for use are black, cyan, magenta and yellow, for example.
Note that all or any one of four recording heads constituting recording means is indicated by recording means 1 or recording head 1 in the following description.
In FIG. 4, 6 is wiping means (hereinafter referred to as a blade) as a cleaning member for wiping away alien substances by rubbing against a discharge port face of each head, and 51 is capping means for enclosing the head at the time of suction recovery, both of them being held on a recovery base so as to be movable in directions toward and away from the carriage. The capping means 51 held on the recovery base 53 is connected via a suction tube 27 to a suction recovery pump 26. Numeral 7 indicates a carriage position lever.
In such an ink jet recording apparatus with the above constitution, after recording with the ink jet head, or after interruption of the recording, the ink jet head is moved from a recording region to a non-recording region (thereinafter referred to as a home position) where the head is placed opposite to the cap, and stopped therein, and the cap is moved closer to the carriage to make a capping. And after the capping is made, a suction recovery operation is performed by using the suction pump 26. Also, when the carriage is moved to the home position, the wiping member 6 is projected outward in a direction toward a plane containing the ink discharge port of the head (thereinafter referred to as a head face plane) to make a wiping operation by rubbing against the head face plane.
Referring now to FIG. 5, Numerals 1, 31, 32, 51 and 53 in the figure are the same as those in FIG. 4. Numeral 7 is a carriage position lever (hereinafter referred to as a lever), with its lower end portion provided in contact with a carriage guide rail, and the position of the carriage can be determined by means of this contact portion and the carriage guide pipe. Accordingly, the position of the carriage is controllable by changing the position of the lever 7. In FIG. 5, three different lever positions of A, B and C are indicated. In FIG. 5, Numeral 61 is a wiping blade (hereinafter referred to as a blade) composed of an elastic member, 62 is a blade base, 63 is a presser spring for securing the blade 61 to the blade base 62, and 64 is an absorbing body plate arranged close to the blade 61 and for removing the blade adherent ink. The wiping member 6 comprised of 61, 62, 63 and 64 is attached to the side of the recovery base 53 so as to be movable in directions toward and away from the carriage.
In such an ink jet recording apparatus, to control precisely the wiping condition, in particular, the amount of penetration of the wiping member into recording head, it was the common practice to place the recording head at the same position at any time in a region where the wiping was performed. That is, the position of recording head might vary between the print region and the wiping region (normally contained in a recovery operation region).
However, in such an ink jet recording apparatus, in conducting the wiping operation during the printing, the carriage is moved in both the wiping region and the print region, whereby there was a risk of causing such a malfunction that the printed image was distorted or the pressure variation was produced in the ink within an ink supply channel, thereby making the discharge unstable, due to the vibration of the carriage produced by the change of position. Therefore, in the conventional ink jet recording apparatuses, a countermeasure against the malfunction was taken by providing an approach region sufficient to receive the vibration between the wiping region and the print region, or a position changing region to enable the position change gently, but such a provision resulted in a larger main body with a more complex mechanism.
That is, conventionally, in the ink jet recording apparatus having a carriage settable at a plurality of positions, it was difficult to make the main body smaller while maintaining high image quality and high reliability.
The present inventors have found, as a result of minute examinations to solve the above-mentioned problems, that there occurs a difference in the cleaning characteristic depending on the rubbing state between the wiping member and the ink jet head.